1. Field of the Disclosure
The disclosure herein relates generally to an apparatus and a method for displaying images.
2. Background Information
Spatial light modulators, which typically perform a form of spatial-variation on a property of a beam of light, such as its phase, intensity, etc., are used in sequential color display systems to project images for various video media sources such as High Definition Television (HDTV), Digital Video Disc (DVD) players, and Digital Visual Interface (DVI) devices. Viewers generally evaluate display systems based on criteria such as image size, resolution, contrast ratio, color purity, and brightness. Image brightness is a useful metric because the available brightness can limit the size of the projected image and because it can also control how well the image can be seen in high levels of ambient light. The brightness of a given projection display is sometimes increased by increasing the size of the light source used to form the image. However, increasing the size of the light source also increases the cost, size, and weight of the entire display system. Additionally, larger light sources generate undesirable additional heat.
Another approach to increasing the brightness at the display has been to use an inherently brighter light source, such as a laser. However, the use of laser illumination in projection display systems often results in a substantially random spatial intensity modulation known as “speckle.” Speckle arises when viewing a coherent light, such as laser light, on a screen which is rough compared to the wavelength of the coherent light. The term “rough” typically means a surface whose local irregularities in depth are greater than one quarter of the wavelength of the coherent light. The appearance of speckle can vary as a viewer's head moves in relation to the screen, which can make the appearance of speckle even more objectionable. Thus, there is a need for a projection display system that can reduce speckle.